Bone conduction is the conduction of sound to the inner ear through the bones of the skull, and a bone conduction hearing aid, or bone conductor, is a device that stimulates through bone conduction. Other types of hearing aids may instead directly stimulate the tympanic membrane, the middle ear ossicles, the round window, the oval window or the cochlear fluid. Several different types of bone conduction hearing aids are available. A bone conduction hearing aid may amplify sound or it may also work as a tinnitus masker. A bone conductor may also be used in audiometry to determine bone conduction hearing thresholds. Current bone conductors include however several drawbacks, as described below.
The traditional bone conductor consists of a hearing aid with a vibrator that is pressed against the head behind the ear by a spring arrangement extending from the other side of the head. The steel spring arrangement is sometimes built into an eyeglass frame. The vibrations are transmitted through the skin and the skull bone into the inner ear. For the traditional bone conductors with a spring arrangement around the head, the constant pressure against the skull bone often causes headaches and skin irritation. A constant pressure against living tissue tends to lead to poor blood supply and irritation. The spring arrangement is also bulky and is not a practical or user friendly solution.
Another type of established bone conductor, which is sometimes called a direct bone conductor, includes a vibrator, which is directly and firmly connected to an anchoring component that is anchored to the skull bone through which the vibrations are directly transmitted from the vibrator to the skull bone. The vibrations do not pass through the skin on its way from the vibrator to the skull bone. This type of bone conductor may be designed with a permanent skin penetration which may lead to problems with skin infections. If this type of bone conductor is instead designed with an implanted vibrator and where energy are transmitted from an external hearing aid there is a significant energy loss when transmitting the energy with an inductive link through the skin. Another drawback is that the vibrator cannot easily be repaired if it breaks down.
To avoid the need for surgery or bulky spring arrangements, adhesively attached bone conductors have also been suggested, however these have not become successful. To transmit the vibrations to the skull, these suggested adhesive bone conductors includes a protruding portion pressing towards the skin. The pressure is achieved by the surrounding adhesive attached to the skin. The drawbacks are that there will still be a constant pressure against the skin and the arrangement tends to come loose since there will be a constant force trying to remove the adhesive from the skin since it is the adhesive is counteracting the pressure force from the protruding portion. To try to adjust this type of device the protruding portion is made adjustable with a screw to try to make it work and the arrangement then becomes more complex and expensive due to its design. Other suggestions such as taping the bone conductor to the head have not become successful arrangements. Some of these arrangements also required removal of the adhesive from the skin to remove the bone conductor which may cause too frequent stress on the skin.
Another type of bone conductor is a type where the vibrator is placed in an external unit outside the skin and where this external unit is kept in place through a magnetic attachment to a part that is anchored to the skull bone and implanted under the skin. In this arrangement, the signal from the external part is passing through the skin to the implanted part and the skull bone. For this type of bone conductor, surgery is still required and the pressure towards the skin may cause skin necrosis due to the constant pressure against the skin. When a magnetic attachment is used, the hearing aid may also easily fall off.
For all non-surgical bone conductors, the firmly established design tradition has been that the arrangement has to include some sort of member creating a pressure against the skin to obtain a sufficient transmission of the vibrations from the vibrator to the skull. Applying a pressure against the skin improves the transmission through the skin. With an improved transmission through the skin, the hearing aid with the vibrator, electronics and battery can be made smaller and does not have to be as powerful as if there were no pressure against the skin. There has been a long tradition in the industry of trying to make the hearing aid systems as small and as light-weight as possible for the convenience of the user. Due to this strong trend and tradition, the industry has been completely focused on designs that require that a pressure against the skin must be created by the hearing aid system. This has almost been a dogma. In spite of many efforts during several decades, no system has become successful because the pressure makes the device fall off, irritates the skin or becomes complicated particularly when adjustable arrangements are used. Since pressure against the skin in an adhesive bone conductor has to, in some way, include a protruding area or component, previous solutions have not included any kind of soft rubber portions to follow the curvature of the head of the individual since such portions would not contribute to the creation of a pressure against the skin.
For conventional adhesive bone conductors, the coupling between the hearing aid and the adhesive carrier has been placed at the center of the carrier. The coupling has been placed at the center to reduce the risk of the adhesive coming loose from the skin due to the weight of the hearing aid. However, the general anatomy of the hair free area behind the ear is such that the placement of the coupling at the center results in the coupling and the hearing aid touching the outer ear causing undesirable acoustic feedback and discomfort.
Furthermore, the industry has been completely focused on arrangements where only the adhesive component in itself has been the disposable single-use component that has been replaced when it does not adhere well to the skin anymore. It has been the established design tradition to have a complex component carrying the adhesive component. A double-sided adhesive-sheet, for example, is inexpensive but it is difficult for the patient to replace it on the carrier and the remaining adhesive disposed around the edges often collects dirt and bacteria. There is a need for a more effective bone conduction hearing aid system that is reliable and does not have the drawbacks discussed above.
The present invention provides an effective solution to the above-outlined problems of bone conduction hearing aids. More particularly, the bone conduction hearing aid system of the present invention has a hearing aid device with a vibrator disposed in a hearing aid housing. The hearing aid device has a first connection portion. Furthermore, the bone conduction hearing aid system of the present invention has an interconnection unit that has a contact plate portion and a second connection portion. The second connection portion is located on a first side of the contact plate portion. The contact plate portion has a second side at least partly provided with an adhesive component. The second side is configured to, when in use, face a skin of a user of the bone conduction hearing aid system. The first connection portion of the hearing aid device is connectable to the second connection portion of the interconnection unit so that these two portions form a coupling. The adhesive component has a first adhesive side and a second adhesive side. The first adhesive side is attached to the second side of the contact plate portion and the second adhesive side is adhesively attachable to a skin of a user. The present invention allows the interconnection unit with the adhesive component to be at least partly positioned between the hearing aid device and the skin of the user to enable a practical and cosmetic solution. The present invention also allows the hearing device to be connected to and disconnected from the interconnection unit without having to, at the same time, connect or disconnect the interconnection unit to the skin of the user. The contact plate portion and the second connection portion are made in one piece continuous injection molded polymer material and this unique design makes it possible to manufacture the entire interconnection unit in one injection molded part with an attached adhesive component which makes it possible to do the interconnection unit as a low cost disposable component.
The second connection portion protrudes from the first side of the contact plate portion which makes it easier to locate the second connection portion when connecting the hearing aid to the interconnection unit. In the present invention, one of the first and the second connection portion is a female connection portion and the other one of the first and the second connection portion is a male connection portion. The male connection portion is at least partly insertable into the female connection portion and one of the female and male-connection portion is flexible with a snap-in ridge and the other of the first and the second connection portion having a circular rigid coupling ridge to ensure a secure retention when attached. In the bone conduction hearing aid system of the present invention the second side of the contact plate portion is concave or planar without convex areas and without protruding means from the interconnection unit, i.e. there are no protruding parts or portions designed to cause specific pressure against the skin. This unique design is critical for the success of the invention since this offers a much more secure adhesive retention of the hearing aid system than if the adhesive would have to counteract a specific pressure against the skin. The lack of specific pressure against the skin is also more skin friendly. Our research has surprisingly shown that bone conduction vibrations can be successfully transmitted from an external vibrator to the skull also without any pressure applied to the skin. The reason for this successful transmission may be due to the incompressibility of skin tissue which might not have been fully considered before.
The interconnection unit of the bone conduction hearing aid system of the present invention has preferably a weight lower than 2 grams and the contact plate portion has preferably at least 5 through holes to enable moist transportation and these holes also contribute to keeping the weight down.
In a preferred embodiment of the bone conduction hearing aid system of the present invention, the second connection portion is positioned non-centrically on the first side of the contact plate portion so that a front end of the contact plate portion extends at least twice as far out from a center point of the second connection portion compared to the extension of a rear end of the contact plate portion. These proportions are essential to use the non-hair-bearing area behind the ear for adhesion and still enable a suitable attachment of the hearing aid device without interfering with the outer ear.
In a preferred embodiment of the bone conduction hearing aid system of the present invention, the first connection portion is a rigid female connection and the second connection portion is flexible male connection and wherein the flexible male connection portion has at least two flexible spring arms having a snap-in ridge at a connection end of the spring arms.
In a preferred embodiment of the bone conduction hearing aid system of the present invention, the second connection portion is a rigid male connection portion protruding a distance out from the first side that is at least the 50% of an average thickness of the contact plate portion. These proportions are essential both to keep the thickness of the contact plate portion down and to ensure an efficient function of the second connection portion.
In a preferred embodiment of the bone conduction hearing aid system of the present invention, the contact plate portion has a flexible peripheral frame around at least part of the periphery of the contact plate portion so that it can be more easily adapted to a curvature of the head of a user. The contact plate portion is preferable still fairly rigid to offer a stable base for the use of the second connection portion.
In a preferred embodiment of the bone conduction hearing aid system of the present invention, the contact plate portion is at least partly transparent to allow at least one of visible light and UV light to be transmitted through the contact plate portion to the adhesive component.
In a preferred embodiment of the bone conduction hearing aid system of the present invention, the adhesive component has a light sensitive switchable release agent that is transformable to change at least the adhesive component of the second adhesive side from a high adhesive state providing a high adhesive strength to a low adhesive state providing a low adhesive strength that is lower than the high adhesive strength. With this design it is possible to minimize the stress on the skin when tearing off the interconnection unit from the skin.
The contact plate portion and a second connection portion of the present invention is preferably manufactured in a single injection molding cavity having a shape of the contact plate portion and the second connection portion together. A melted polymer is then injected into the cavity, thus forming a contact plate portion and a second connection portion in one unit made of the polymer, and then the unit is ejected from the molding cavity after cooling down.
The hearing aid device can be standardized since the coupling to the interconnection unit can be the same for more or less all patients which is important since the hearing aid is quite expensive. The interconnection unit that is more frequently changed and cost efficient to manufacture can, however, easily be manufactured in various shapes and sizes to fit different users.
The present invention is unique since it works without any protruding parts in the adhesive area that cause pressure against the skin. Because the skin pressure is minimal, the retention is secure and skin friendly. The design of the present invention enables an adhesive interconnection unit to be cost-efficiently produced as a single use disposable component which is important for practical and cost aspects.
The present invention goes against the established design tradition. One drawback of the present invention is that it requires a more powerful hearing aid device since it works without any pressure against the skin. As explained above, conventional thinking in the hearing aid industry has been to focus on minimizing size and weight and therefore prior art designs have relied on applying a pressure against the skin because that improves the conduction from the hearing aid devices into the skull of the user and thus make it possible to use small and light-weight devices. Another drawback of the design of the present invention is that there is no adjustable member that could be used to create and adjust the pressure against the skin in case a patient prefers more power at some time. However, it has surprisingly been found that the advantages of reduced risk of fall off the skin, less skin irritation and less complicated design requirements outweigh the drawbacks of the need for a more powerful hearing aid device that is heavier and bigger than conventional designs. Although the hearing aid device of the present invention needs to be more powerful and is therefore usually bigger and heavier compared to conventional designs , the retention is still more secure and it is more skin friendly compared to conventional design that requires a constant pressure against the skin. A somewhat heavier hearing aid device of the present invention may also be compensated by the fact that the interconnection unit can be made very light when it is an integrated part without adjustable parts, and therefore the total weight of the arrangement carried by the adhesive may still be similar to conventional designs.
The interconnection unit of the present invention where the contact plate portion and the second connection portion are made integral enables the entire interconnection unit to be a cheap disposable component. This is a key to make the arrangement hygienic and practical to handle. A drawback of the present invention is that the interconnection unit is a more expensive disposable component than if only the adhesive component was changed when the adhesive does not adhere sufficiently to the skin anymore. However, surprisingly the advantages of replacing the entire unit instead of just the adhesive sheet outweigh the drawbacks of higher costs since it is much more practical for the patient and the replacement of the entire unit significantly improves the hygiene. Also, the material of the interconnection unit is preferably recycled for environmental purposes.
The solution of the present invention go against several established design parameters as described above and the result is a surprisingly excellent hearing aid system where the advantages outweigh the drawbacks and the present invention provides valuable improvements in hearing rehabilitation.
As described above, the bone conduction hearing aid system of the present invention includes a unique combination of solutions and provides new solutions and several advantages to meet complex user requirements.